Impulse 7108 - Manual (Page 15)

Appendix D - Ground Loop Phenomenon
Sealevel Systems ULTRA COMM+I.LPCI Page 13
Appendix D - Ground Loop Phenomenon
What is Ground Loop?
Ground loop Phenomenon occurs when two (or more) pieces of equipment are connected together with a common
ground and a different ground potential exists at each location. This current can cause the connected equipment to
experience noise that in turn causes data transmission errors. In the extreme this ground current can cause equipment
malfunction or even destruction.
Cabling Recommendations
When connecting the ULTRA COMM+I.LPCI in a RS-485 network, care should be taken that both ends of the
network are not isolated from ground (see Figure 8). This “floating” ground condition could cause the capacitive or
inductive coupling of voltages that will cause a break down in the DC to DC converter circuit or in the opto-isolator
circuit. This condition will cause data errors and possibly destruction of the receiver circuit.
A B
Isolation
Barrier
DATA+
DATA-
Ground
Isolated
Adapter
Non
Isolated
Adapter
Figure 8 – ULTRA COMM+I.LPCI cabling example